What am I missing with managing traffic

I just started playing Cities: Skylines 2, and it's pretty cool. Seems like a good mega time-sink game. But oh man is managing traffic flow DIFFICULT. I'm beginning to understand how the AI behaves whenever it comes to types of intersections, like oh man is the computer bad with changing lanes at the last minute or what.

But what I'm working on right now is figuring out how to manage my larger traffic volumes. I've gotten a couple cities to get to 10k-20k population, but around that point I have the same issue with traffic flow, in that I don't know a space efficient way to distribute high volume traffic in my city on my roadways. I think the issue is I'm just getting too high of a population too quickly. I think I'm also making neighborhoods that are WAAAAAAAAAAY too large. How large do you all usually make your large apartment neighborhoods?

Edit: Okay so additional parking makes traffic MUCH worse. I kept thinking "oh man, this is a TON of apartments, so they all need parking for their cars!" If you put 10 underground parking garages next to it, hundreds of cars will spawn and swarm at you in droves, bloodlust in eyes.